title: Synthesis of 1-vinylidene-naphthofurans: a thermally reversible photochromic system that colors only when adsorbed on silica gel.
abstract: A set of new 1-vinylidene-1,2-dihydro-naphtho[2,1-b]furans were unexpectedly obtained in the reaction of 2-naphthol with readily available 1,1,4,4-tetraarylbut-2-yne-1,4-diols. Surprisingly, when adsorbed in silica gel, these compounds exhibit photochromism at room temperature, whereas not in solution and in the solid state. UV or sunlight irradiation leads, in a few seconds, to the formation of intense pink/violet to green colors that bleach completely in a few minutes in the dark. These new compounds also exhibit reversible acidochromic properties in solution: addition of TFA leads to the opening of the furan ring and addition of a proton to the allene function, leading to a conjugated and violet tertiary carbocation that returned immediately to the uncolored allenic structure upon addition of a weak base.
authors.affiliation: Centro de Química-Vila Real, Universidade de Trás-os-Montes e Alto Douro, 5001-801 Vila Real, Portugal.
authors.forename: Céu M
authors.initials: CM
authors.lastname: Sousa
authors.forename: Jerome
authors.initials: J
authors.lastname: Berthet
authors.forename: Stephanie
authors.initials: S
authors.lastname: Delbaere
authors.forename: Paulo J
authors.initials: PJ
authors.lastname: Coelho
mesh_terms: D000327:Adsorption; D003116:Color; D005663:Furans / Q000138:chemical synthesis* / Q000737:chemistry; D005782:Gels / Q000737:chemistry*; D015394:Molecular Structure; D055668:Photochemical Processes; D012822:Silicon Dioxide / Q000737:chemistry*; D013472:Sunlight; D013499:Surface Properties; D013696:Temperature; D014466:Ultraviolet Rays; D014753:Vinyl Compounds / Q000138:chemical synthesis* / Q000737:chemistry
chemical_list: D005663:Furans; D005782:Gels; D014753:Vinyl Compounds; D012822:Silicon Dioxide